全文获取类型
收费全文 | 17103篇 |
免费 | 1978篇 |
国内免费 | 1097篇 |
专业分类
电工技术 | 3534篇 |
综合类 | 1323篇 |
化学工业 | 1768篇 |
金属工艺 | 871篇 |
机械仪表 | 814篇 |
建筑科学 | 1054篇 |
矿业工程 | 523篇 |
能源动力 | 1011篇 |
轻工业 | 1193篇 |
水利工程 | 694篇 |
石油天然气 | 946篇 |
武器工业 | 92篇 |
无线电 | 2117篇 |
一般工业技术 | 1458篇 |
冶金工业 | 786篇 |
原子能技术 | 497篇 |
自动化技术 | 1497篇 |
出版年
2024年 | 108篇 |
2023年 | 320篇 |
2022年 | 636篇 |
2021年 | 758篇 |
2020年 | 676篇 |
2019年 | 543篇 |
2018年 | 508篇 |
2017年 | 639篇 |
2016年 | 692篇 |
2015年 | 686篇 |
2014年 | 1079篇 |
2013年 | 1252篇 |
2012年 | 1148篇 |
2011年 | 1304篇 |
2010年 | 987篇 |
2009年 | 983篇 |
2008年 | 870篇 |
2007年 | 1051篇 |
2006年 | 915篇 |
2005年 | 808篇 |
2004年 | 669篇 |
2003年 | 534篇 |
2002年 | 564篇 |
2001年 | 429篇 |
2000年 | 360篇 |
1999年 | 290篇 |
1998年 | 214篇 |
1997年 | 198篇 |
1996年 | 170篇 |
1995年 | 147篇 |
1994年 | 136篇 |
1993年 | 94篇 |
1992年 | 71篇 |
1991年 | 67篇 |
1990年 | 44篇 |
1989年 | 48篇 |
1988年 | 41篇 |
1987年 | 24篇 |
1986年 | 25篇 |
1985年 | 19篇 |
1984年 | 15篇 |
1983年 | 8篇 |
1982年 | 23篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1964年 | 2篇 |
1960年 | 1篇 |
1959年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
E.F. Thacher 《Energy Conversion and Management》1985,25(4):519-525
With the object of evaluating its importance to thermoelectric generator design, heat loss is introduced into the standard thermoelectric generator design theory. The theory for both the constant hot and cold junction temperatures model and the constant heat input model are so modified. The modification is first order and, therefore, is limited to small leg heat-transfer coefficients. Numerical results using representative properties show that significant differences can exist between the optimum geometry and performance of a generator idealized as lossless and those of a generator designed by the modified theory. The largest differences occur with the constant heat input model. 相似文献
12.
BINELOCA程序是在吸收国外先进大破口失水事故分析计算机程序的基础上,针对我国现有大破口失水事故分析程序的不足和工程应用方面的问题,采用了一些成熟的、新型的和当今国际公认的瞬态热工水力数学物理模型以及水和蒸汽性质参数计算公式改编而成的大破口失水事故分析程序。通过对广东岭澳核电站大破口失水事故的计算表明,BINELOCA程序计算的结果与法国计算的结果是一致的。 相似文献
13.
电感电容损耗电阻的讨论 总被引:3,自引:0,他引:3
通过对电容电感阻抗的测量,发现实验值偏离理论值。定性地分析了误差的来源,得出的结论是电感电容内部的损耗电阻随着频率的变化而变化,变化方向相反而并非相同。 相似文献
14.
In this paper, the author dipped surface vapor oxidized H13 steel specimens into 700℃ molten aluminum liquid for a certain period of time. Analyze the intermetallic phases formed on the H13 samples surface with optical microscope and X-ray diffraction method. The observation of immersion test sample's cross-section shows that Fe3O4 film will protect die substrate from molten aluminum erosion. The identification of the intermetallic phases reveals that they consist of 2parts, which is named as the composite layer and the compact layer. Further investigations are made in order to know the phase constituents of the 2 layers, they are Al8Fe2Si (outer composite layer), (AlCuMg) and Al5Fe2 (compact layer),respectively. The experimental results show that on the same specimen, a convex surface with bigger radius of curvature is more likely to be molten and the melting loss speed is also faster than a flat and smooth surface. The thickness of compact layer on a smooth surface is much bigger than that of the convex surface. Therefore, the author supposes the compact layer is favorable in stabilizing the die surface material from further melting loss, as their formation on the die surface, the melting loss speed will decrease. 相似文献
15.
D. M. Weaver 《Nutrient Cycling in Agroecosystems》1993,36(2):165-170
Nutrient loss from rural point sources and urban environments need to be minimised as part of strategies to overcome declining water quality on the Swan Coastal Plain and in the Peel-Harvey estuary in Western Australia. This paper discusses the management of nutrient losses from domestic effluent, urban stormwater runoff, domestic gardens and public open space, intensive animal industries and intensive irrigated agriculture. Measures to minimise nutrient losses from these sources are outlined, using cooperative, technological and regulatory approaches. 相似文献
16.
本文由无限稀释活度系数求取混合物MH-81状态方程的二元相互作用参数,预测了二元混合物的汽液平衡,获得了较满意的结果。 相似文献
17.
樊兆峰 《徐州工程学院学报》2011,(2):28-31,48
针对酚水稀释过程中酚水流量不便测量的工程情况,提出了一种基于RBF(径向基)神经网络的预测控制方法.在酚水罐每个液位变化周期内使用计算机定时测量液位高度,并将这些高度值作为目标输出,在每个循环结束时训练RBF网络,利用RBF网络的逼近能力来实时预测酚水流量,从而控制清水的配比,实现酚水质量浓度的稳定.该方法可避免测量误差带来的干扰,提高控制精度. 相似文献
18.
19.
Recently, it has been reported by our group and others1.2 that loss of curing agent is encountered during the curing of small droplets or thin films of amine cured epoxies. In our earlier study3 results were reported on loss of curing agent in small droplets used in conducting the rnicrobond, single fiber test for determination of interfacial shear strength (ISS). It was reported that use of a volatile curing agent (meta-phenylene diamine (m-PDA) with DGEBA resin) resulted in increasing amounts of curing agent being lost (as measured by T8 of the cured droplets) with decreasing droplet size during the processing procedure. Droplets smaller than 150 micrometers were seen to lose up to 40% of the curing agent leading to alteration of the mechanical properties of the droplet and, therefore, causing measured values of ISS to be exceedingly low. Use of a less volatile curing agent (Jeffamine 700, a polyether diamine, Texaco Specialty Chemicals) in combination with DGEBA resin produced results which indicated that loss of curing agent was not occuring. This study was undertaken to show the relationships between film (or droplet) size and the amount of curing agent lost (during the processing) for three different aminecured epoxy systems. 相似文献
20.
张瑞娟 《兰州工业高等专科学校学报》2014,(5):64-67
根据防护费用法、影子工程法等折算办法对环境破坏导致的经济损失等价为具体货币值,并将这些环境影响量化分析计算方法应用于西宝客运专线建设的环境评价问题中.结果表明:提出的算法对铁路选线多目标决策方案比选有应用价值. 相似文献